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The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- urn:nbn:de:bsz:14-db-id1780948042-188300004
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- http://digital.slub-dresden.de/id1780948042-18830000
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- oai:de:slub-dresden:db:id-1780948042-18830000
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- Bandzählung
- No. 1289, May 18, 1883
- Digitalisat
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Zeitschrift
The photographic news
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- Titelblatt Titelblatt I
- Register Index III
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320 THE PHOTOGRAPHIC NEWS. [May 18, 1883. certain number of lines measured by previous observers have been compared with the new measurements. Taking the numbers given by Thale'n, Lecoq de Boisbaudran, and Cornu for 150 lines in the spectra of magnesium, zinc, cadmium, alu minium, indium, thallium, iron, &c., a close agreement with their measurements affords satisfactory evidence of the accuracy of these determinations. Besides the wave-length, a very care ful description of the appearance of each line is given, together with its linear measurement indicating its position on a series of photographs obtained with the prism spectroscope, which series of photographs is presented with the paper. A distinction is drawn between those lines determined directly with the grating, and others too faint to be seen on diffraction photographs, which were measured by the aid of the prism spectroscope, and an interpolation curve 9} metres in length. The total number of lines measured and described is 2,247, namely :—Magnesium, 42 ; zinc, 151; cadmium, 141 ; aluminium, 30; indium, 104 ; thal lium, 70 ; copper, 164 ; silver, 124; mercury, 80; carbon, 20 ; tin,129; lead, 86 ; tellurium, 322 ; arsenic, 112; antimony, 211; bismuth, 156 ; air, 215 ; and iron, 150. A series of eighteen enlarged photographs, 36 inches in length, were produced. The authors describe also a method of taking photographs of diffraction spectra produced by a small Rutherford speculum ruled with 17,460 lines to the inch. The lines in the spectra were accurately measured by the aid of a microscope magnifying 25 diameters, and a dividing engine. The length of the spectra which were taken on three different plates was 14 to 15 inches, and the measurements were accurate to the zoogth of an inch. From these measurements the wave-lengths of the lines were calculated. The spectra include lines with wave-lengths 4,674 and 2,024. They were produced by electric sparks condensed by a pane of glass coated with tin-foil. Wooden Taps.—All wooden taps u ed for chemical purposes may be well preserved by plunging them into a bath of pure paraffin heated to 110% or 1209 C. This temperature must be kept up as long as we perceive any air-bubbles arising from the wood. The bath is then, and then only, allowed to cool gradually, and the taps are taken out just as the paraffin is about to solidify. The excess of paraffin which still adheres to the outside is rapidly wiped off with a cloth, and the tap is finally subjected to an energetic friction with the same cloth. After this treatment an ordinary wooden tap, which, generally speaking, is soon unfit for use, may be preserved for a considerable length of time, and will be found to resist the corrosive action of dilute acids perfectly. Many other objects in daily use in the pharmaceutical laboratory may be ad van - tageously treated in the same manner, and so preserved for a long time from the effects of corrosive liquids, damp, or oxidation.—Burgoyne’s Monthly Magazine. Luminosity of Flam®.—Recent experiments made by Dr. W. Siemens tend to disprove the old notion as to luminosity being due to solid particles heated to a temperature of incan descence. The author demonstrates that the heat-rays emitted from hot gases are very small in number as compared with those emitted from equally hot solid bodies. Observations on the behaviour of flames themselves prove equally that the luminosity of flames is not due to the incandescence of the products of combustion. If the gases to be burnt are more quickly mixed, the flame becomes shorter, since the process of combustion is accelerated, and hotter, since less cold air is mixed with the burning gas. The same phenomenon occurs if the gases are strongly heated before they are burnt; but since the ascending products of combustion are maintained for a short time only at the temperature of the flame, the above phenomenon would be reversed were the gases self-luminous. The luminous part of the flameis separated by a line of demar cation from the products of combustion, and is coincident with the termination of chemical action, which is probably the cause of the emitted light. If it be assumed that the gas molecules are surrounded with an envelope of ether, then a chemical com bination between two or more of these molecules will cause a vibration of the ether particles, which becomes the starting- point of the light and heat waves. The luminosity of gases when an electric current is passed through them can be ex plained in a similar manner, and the author has already observed that all gases are conductors of electricity when their point of so-called polarisation maximum has been reached.— Journal of the Chemical Society. Photographic Club.—The subject for discussion at the next meeting of this Club, May 23, will be “ On the Means of Drying Gelatine Films.” Ol Gorresgouents. *,* We cannot undertake to return rejected communications. J. Thoens.—After sensitising, draw the paper once or twice through distilled water contained in a flat dish ; but the washing must not be so complete as to remove the whole of the free nitrate. Taper thus prepared will keep several months if well dried and preserved in a portfolio between sheets of blotting-paper which have been saturated with a weak solution of carbonate of soda, and dried. The sensitive paper must be fumed with ammonia before use. W. Reynolds.—We have still copies of No. 1286, with which Mr. Dixon’s lion picture is issued. You can have a copy by post for 3]d. H. Spink.—Some scum-like substance, perhaps of a fatty nature, has found its way into the emulsion, perhaps from the use of an imperfectly clarified sample of gelatine. The chemical reduction is a result of the long-continued action of the impurities referred to. We have sometimes found it advantageous to draw off the lower strata by means of a syphon. W. H. P.—1. It makes no difference so long as none is reflected from any substance within range of the lens. 2. Yes, the best results may be obtained in this manner. Thank you for your friendly sentiments; we shall be always pleased to give or obtain any information in our power. S. Horton.—It probably needs drying. Bake it in an oven till it no longer parts with any moisture, and repeat this operation whenever the chloride of calcium shows signs of dampness. Wm. DUNNINGTON.—It is due to the partial separation from the glass, and if you saturate the paper more thoroughly with the paste or the gelatine, so as to thoroughly fill the pores, it will not occur. Alfred Levy.—Write to the Scovill Photographic Company, New York. J. H.—Thanks, it is a very clever idea. A. Bath.—It is probable that the prints to which you refer are enamelled with collodion. Coat a plate with either plain or iodised collodion, and soak in water till all appearance of greasiness dis appears. Plate and print being now immersed in a warm solution of gelatine, containing about 5 per cent., the picture is laid face downwards on the collodionised glass, and contact is established by means of a squeegee. When dry, the print can be readily detached if one corner is lifted with the point of a penknife. E. H. F.—Thanks for your note. W. W. Winter.—Write to Mr. A. L. Henderson, The Studio, King William Street, London Bridge. A. B.—It is difficult to say with certainty, as there may be several patents covering the several mechanical movements involved. Hope.—No conveniences as to actual working arrangements can compensate for the fact of the studio being in a bad locality; and, judging only from the particulars which you give, we would advise you to have nothing to do with it. P. I. Milsom.—The bubbles consist principally of carbonic acid gas, and they usually form in water recently drawn from a moderately deep well. You should brush them*from the surface of the paper occasionally, as they may hinder the free circulation of the fluid. Bristol.—Under the circumstances, it is better to use fine pumice powder. Sift it through the finest muslin, and rub it on the varnished surface with the tip of the finger. C. L.—Not so, as it tends to become lighter in colour when ex posed to a strong light; but if stowed away in a dark place it gradually darkens. Printer.—1. Indian ink is usually added, but not much; about thirty grains of the dry ink to each pound of mixture. 2. Bi chromate of ammonia is to be preferred, as it is not so liable to crystallise in the film ; and we fancy that it is easier to obtain details in the deep shades, than when the potassium salt is em ployed. 3. The splitting off cf the film probably results from the drying having been effected at too high a temperature; do not let the heat rise above 40% Centigrade. An addition of glycerine is hardly to be recommended. Printer.—1. The sample of paper is quite unfit for use, as the albumen has undergone decomposition. 2. Thin glue is a very convenient material. 3. It is not a process which c m be worked satisfactorily at odd times; and if you go in for it, you must mako up your mind for constant and hard work. Still, you will be well repaid if you persevere. PHOTOGRAPHS REGISTERED. Mr. D, Whyte (Inverness}—Photo, of Lady Florence Dixie.
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